Various monitoring systems are in the actual use to watch an unattended shop or office at night and protect it from suspicious people or invaders or to monitor a place that is dangerous or inaccessible by people. In this kind of monitoring system, a data transmission/reception system of a so-called client-server type is used. This type of data transmission/reception system is made of at least one data-transmitting terminal and a data-receiving server connected thereto via cable or wireless network.
In this data transmission/reception system, various sensors that detect various states of subjects to be monitored, such as a camera and thermometer, are mounted on its data transmitter. The data collected from such a sensor is transmitted to the data-receiving server. The data-receiving server shapes the data transmitted by the data-transmitting terminal into predetermined formats and accumulates them in its database.
Some patent applications of monitoring systems have been filed. Japanese Patent Application Non-Examined Publication No. H09-288684 discloses a monitoring system that regularly transmits to an image-collecting server image data acquired by a camera disposed at a place to be monitored, and automatically updates image data on a Web page.
European Patent Application EP0986259A2 discloses a structure of a network camera monitoring system having a motion detection means. In this structure, image data are transmitted when the motion detection means detects a moving object.
Japanese Patent Application Non-Examined Publication No. 2000-59759 discloses a monitoring camera system that processes images taken by a monitoring camera, and displays and accumulates the image data only when an abnormality is detected.
Japanese Patent Application Non-Examined Publication No. 2000-4272 shows a data transmission/reception system utilizing meta data and discloses a structure that coverts accumulated meta data into a format suitable for transmission.
In these conventional monitoring systems, the format of the data accumulated in the database is defined as a format inherent in each system and thus general use of the accumulated data is difficult.
The data-receiving server performs analysis (e.g. format conversion) on received data for accumulation in the database. When a large number of data-transmitting terminals that collect different types of data are connected, the data analysis imposes a heavy load on the server.
In addition, when encoded image data are transmitted or received, how to control attribute information attached to the image data, such as the encoding scheme, image size, recording time, recording period of time and imaging position, poses a problem. In a conventional data transmission/reception system, a header including the image attribute information is added to the head of the image, or image attribute information including information linked to the image data is generated and the image attribute information is managed in a database independently of the image data. However, with these methods, the data format having high dependability on the system deteriorates mutual connectivity with other data transmission/reception system.
Furthermore, when a data transmission/reception system is used for remote supervision, a huge amount of image data put a large burden on an operator monitoring the image and make the amount of image data accumulated in the database huge.